1. Field of the Invention
The present invention relates to a method of manufacturing a thin film transistor (“TFT”) substrate with excellent characteristics by using a three-mask process.
2. Description of the Related Art
An active matrix display device such as a liquid crystal display (“LCD”) device or an organic light emitting display (“OLED”) device includes a plurality of pixels which are arranged in a matrix form. Each of the pixels includes an electric field generating electrode and a switching element.
As a switching element, a TFT which is a three-terminal element including a gate, a source and a drain is usually used. The TFT transmits a data signal applied to the source to an electric field generating electrode in response to a gate signal applied to the gate electrode.
Such a display device further includes gate lines and data lines which transmit signals to the TFTs. The display device includes a TFT substrate on which the electric field generating electrode, the TFTs, the gate lines, and the data lines are formed.
The TFT substrate has a multi-layer structure in which a plurality of conductive layers and a plurality of insulating layers are stacked. The TFT substrate with the multi-layer structure is manufactured using several photolithographic processes and subsequent etching processes.
A photolithographic process includes complicated steps such as a deposition process, a cleaning process, a photoresist coating process, a light exposure process, a developing process, an etching process, and a photoresist strip process, and thus a defect may occur in the TFT substrate during the photolithographic process. Accordingly it is desirable to reduce the number of photolithographic processes employed.